Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Patent
1996-04-29
1998-06-02
Lee, Benny
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
333219, H01P 1203, H01P 708
Patent
active
057606650
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a stripline resonator structure comprising a substrate and one or more stripline patterns formed on the substrate as a conductive coating.
Stripline resonators are low planar resonators. They are used in the implementation of high-frequency circuits, e.g. in mobile phones or their base stations. Stripline resonators can be used e.g. at the output stages of mobile radio amplifiers as matching circuits and filtering circuits. Stripline circuits are used generally already at frequencies of 1.8 GHz. The stripline patterns of stripline resonators are matched with each other in such a way that the resonator structure will provide a frequency response of a desired kind within the frequency range. At simplest, the resonator structure may be formed by a single stripline pattern. This kind of resonator can be used e.g. with a voltage-controlled oscillator (VCO), where the stripline resonator determines the oscillating frequency of the oscillator. In the case of a duplex filter, stripline resonators usually comprise 3 to 6 stripline patterns or 6 to 12 stripline patterns. The properties of the stripline resonator, that is, in practice, the resonance frequency and specific impedance, depend on the width and length of the stripline pattern, the distance between adjacent stripline patterns, the thickness of the substrate, and the dielectric constant of the substrate.
The substrate of stripline resonators is of a dielectric material, such as a ceramic material, e.g. Zirconium tin-titanate having a dielectric constant of about 36 units. Stripline patterns are formed on the substrate by conductive metallization, such as a silver coating. Stripline resonators are used mainly due to the fact that they are easy to produce and low in structure. By the use of the stripline resonator, a desired resonator structure can be made lower, and, in any case, it is easier to produce than with another resonator type, i.e. coaxial resonator, which, however, provides a higher quality factor (Q factor) than stripline resonators.
In conventional stripline resonators known from the prior art, stripline patterns are formed on an even substrate as thin planar strip-like patterns. In the prior art stripline resonators, the stripline pattern is extremely thin, frequently having a thickness as small as a few tens of micrometers. In practice, the stripline pattern, i.e. the conductive coating, is thus a two-dimensional planar pattern. The biggest disadvantage of the prior art stripline resonators is that they have a low Q factor as compared with Q factors attainable by coaxial resonators, for instance. The low Q factor of stripline resonators is due to line losses occurring in stripline patterns. Other problems associated with prior art stripline resonators implemented by planar two-dimensional stripline patterns concern the electric matching, or coupling, between adjacent stripline patterns, and the provision of external coupling. In prior art solutions, coupling between adjacent stripline patterns, i.e. individual resonators, has been adjusted by varying the distance between the adjacent stripline patterns, which, of course, has increased the physical size of the stripline resonator as an individual component.
Attempts have been made to improve the properties of stripline resonators by shaping the stripline patterns of the stripline resonator structure so as to make them three-dimensional to some extent, thus operationally imitating the coaxial resonator allowing a higher Q factor. An example of such a structure is a resonator structure where semi-circular arched recesses are formed in a planar substrate, the stripline coating being formed on the surface of the recesses. However, the Applicant has observed that this solution does not provide a sufficiently suitable structure for all uses as far as the ease of production and the imitation of the operation of the coaxial resonator are concerned.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a new stripline resonato
REFERENCES:
patent: 4757286 (1988-07-01), Konishi et al.
patent: 5124675 (1992-06-01), Komazaki et al.
patent: 5160905 (1992-11-01), Hoang
Patent Abstracts of Japan, vol. 10, No. 279, E-439, Abstract of JP 61-100002 (Matsushita Electric Inc. Co. Ltd.) 19 May 1986.
Jantunen Heli
Turunen Aimo
ADC Solitra Oy
Lee Benny
Summons Barbara
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